Process for the preparation of decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene and functionalized derivatives

ABSTRACT

A process for the preparation of compound of formula (I A), decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]accnaphthylene and the corresponding functionalized compounds of general formula (I), intermediates for the preparation of 1,4,7,10-tetraazacyclododecane (II A) and corresponding derivatives (II), by preparation of compounds of general formula (III) and subsequent reduction thereof.

This application was filed under 35 U.S.C. 371, and is the U.S. NationalStage of PCT/EP01/04092, filed 10 Apr. 2001.

The present invention relates to a novel process for the preparation ofthe compound of formula (I A)decahydro-2a,4a,6a,8a-tetraazacyclopent-[fg]acenaphthylene, and of thecorresponding functionalized compounds having formula (I),

used for the preparation of 1,4,7,10-tetraazacyclododecane (II A)

and of the related derivatives (II), through preparation and reductionof the compounds of general formula (III), comprising the steps shown inScheme 1:

The preparation of 1,4,7,10-tetraazacyclododecane (commonly namedCyclen) (II A) according to the present invention is an alternative tothe conventional procedure by Richman-Atkins (see for example J. Am.Chem, Soc., 96, 2268, 1974), which is at present industrially used forthe production of compound (II A), in the form of the sulfate salt.

1,4,7,10-Tetraazacyclododecane is the precursor for the synthesis ofmacrocyclic chelating agents for metal ions.

In particular, the complexes of said chelants with paramagnetic metalions, especially with the gadolinium ion, are characterized by highstability and can be used in the diagnostic field of the nuclearmagnetic resonance technique.

Two gadolinium complexes, Dotarem® and Prohance®, at presentcommercially available and having a chemical structure based on Cyclen,as well as other complexes, are being studied.

It is therefore highly desirable to provide a process for thepreparation of said intermediate which is advantageous both from thecosts and environmental standpoints, avoiding for example thepreparation of the amine tosyl derivatives commonly used in theconventional Richman-Atkins synthesis.

WO 97/49691 disclosed a process for the preparation of compound (II A)by the steps shown in Scheme 2, in which the compound of formula (I A),decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene, is the keyintermediate for the formation of compound (II A), and is obtainable bycyclization of the intermediate (IV),octahydro-3H,6H-2a,5,6,8a-tetraazacenaphthylene, which can in its turnbe prepared from triethylenetetramine and glyoxal.

In Scheme 2, Y is —OH (glyoxal hydrate) or [—SO₃ ⁻Na⁺] (Bertagnini'ssalt) and X is halogen or a sulfonyloxy group

Said process has however some drawbacks. The use of a halogenatedalkylating agent such as 1,2-dibromoethane or 1,2-dichloroethane (scheme2, step a) in the condensation step, although not involving particularsupplying problems, requires specific precautions during use.1,2-Dichloroethane is in fact a cancerogenic, flammable compound whichis used in strong excess in this process. This makes the recovery of thereaction solvent free from 1,2-dichloroethane difficult. Moreover thereaction yield is not very high.

Furthermore, ethylene glycol sulfonic esters have to be prepared, asthey are not commercially available, and they involve the unavoidableproduction of wastes containing sulfonic acids (methanesulfonic,paratoluenesulfonic) which are to be discharged on industrial scale.

It has now surprisingly been found, and this is the object of thepresent invention, a process for the preparation of compounds of generalformula (I), comprising the steps shown in

in which X₁, X₂, R, R₁, R₂ and A have the meanings shown below.

In particular, the process for the preparation of the compounds ofgeneral formula (I)

in which the groups R are both hydrogen, or one is hydrogen and theother is a straight or branched C₁-C₄ alkyl group, optionallysubstituted with one or more —OPg-protected hydroxy groups, in which Pgis a hydroxy-protecting group, comprises:step a) reacting a compound of general formula (IV),

in which, when the groups X₁ are hydrogen, the groups X₂ form a—CH₂—CH₂— group, or vice versa, the groups X₁ are a —CH₂—CH₂— group whenthe groups X₂ are hydrogen, with a compound of general formula (VI)

in which A is a group of formula —COR₁ or —CHRR₂ wherein R has themeaning defined above, R₁ is halogen or C₁-C₄ alkoxy and R₂ is a leavinggroup such as halogen or sulfonyloxy, in at least unitary molar ratio,at a temperature above 50° C.;step b) reducing the compounds obtained from step a), having generalformula (III)

in which one of Y₁ or Y₂ is —CH₂—CH₂— and the other is —CO—CO— or agroup of formula —COCHR, wherein R has the meaning defined above, in thepresence of an amido-reducing agent.

The compounds of formula (I) resulting from the reduction reaction atstep b) of Scheme 1, can conveniently be transformed into1,4,7,10-tetraazacyclododecane derivatives (II A) having general formula(II), according to the procedure disclosed, for example, in WO 97/49691.

In the process shown in Scheme 1, compounds (IV) are prepared asdescribed in WO 97/49691.

Step a) of Scheme 1 consists in condensing compounds (IV) with compounds(VI), operating under inert gas atmosphere (e.g. nitrogen), using atleast 1 mol of compound (VI) per mol of compound (IV), at a temperatureabove 50° C., preferably in a range of 60 to 75° C.

The reaction can be carried out without solvent or in the presence of asolvent, which is preferably selected from: aromatic inert, aproticdipolar or straight or branched C₁-C₄ alcohols and polyethers. Preferredsolvents are selected from the group of: toluene, dimethylacetamide,dimethylformamide, N-methylpyrrolidone, DMSO, C₁-C₄ alcohols as definedabove, glyme and diglyme. Alcohols are particularly preferred.

The reaction time ranges from 0.5 to 36 hours, depending on the solventand the experimental conditions.

In a further aspect of the present invention, the process described inScheme 1 can be carried out, without significantly changing theconditions described above, by using in step a) a catalyst which has asurprising effect on the progress of the reaction.

Significant decreases in reaction times and advantageous increases inyields are in fact obtained, as it will be shown in the experimentalsection.

Catalysts are selected from alkali or alkaline-earth metal salts ofanions of straight or branched C₁-C₄ alcohols, or heterocyclic aromaticbases.

Said catalysts are preferably selected from the group consisting ofsodium methoxide, sodium ethoxide or one of the compounds of formula:

Sodium methoxide and 2-hydroxypirydine are particularly preferred andused in amounts ranging from 0.01 to 2 mol per mol of compound (IV).

Preferred compounds of formula (VI)

are those in which:

-   when R₁ is a halogen or a methoxy or ethoxy group; then A is a group    of formula —COR₁ in which R₁ is a halogen or a methoxy or ethoxy    group, or a —CHRR₂ group in which R is as defined above and R₂ is a    leaving group, such as a halogen or a sulfonyloxy group.

Particularly preferred are the compounds of formula (VI), in which:

-   when R₁ is methoxy, ethoxy, chlorine or bromine; A is a group of    formula COR₁ or a CHRR₂ group, in which R₁ is chlorine, bromine, or    a methoxy or ethoxy group; R is as defined above and R₂ is a leaving    group, such as chlorine, bromine or a sulfonyloxy group.

The compounds of formula (VI) are preferably added in amounts rangingfrom one to four mol per mol of compound (IV).

The compounds of general formula (III) resulting from the condensationreaction at step a) of Scheme 1 can be isolated from the solution uponcompletion of the reaction, either in the salified form with aninorganic acid (e.g. halo acid) or as the free base, and can both berecovered with usual crystallization and/or precipitation techniqueswith organic solvents. Particularly suitable are, for example, n-hexane,toluene, methanol, ethanol and n-butanol.

Compounds (III) are preferably isolated in the salified form, as thehydrochloride, sulfate or phosphate salts.

At step b) of Scheme 1, compounds (III) are reduced to yield thecompounds of general formula (I).

The reduction is carried out by using typical amido-reducing agents. Thereaction is usually carried out in dry medium and under inert gasatmosphere. Examples of methods useful for the reduction of amidescomprise the use of sodium bis(methoxyethoxy)aluminum hydride, LiAlH₄,NaBH₄ in the presence of other reagents, other hydrides and hydridecomplexes, the catalytic hydrogenation on platinum oxide and in solutionof HCl, borane or its adducts with THF (tetrahydrofuran) or DMS(dimethylsulfide).

Sodium bis(methoxyethoxy)aluminum hydride, commercially known asVitride® or Redal®, is preferred, as it is particularly effective.

The reduction reaction is generally carried out by adding compounds(III) to the solution containing the reducing agent, which is added as a70% toluene solution, in amounts ranging from 3 to 4 mol per mol ofcompound (III), and at a reaction temperature ranging from 35° C. to thetoluene reflux temperature.

The reduction reaction is preferably carried out at the refluxtemperature of the solution for 1.3 hours, using at least 3 mol ofsodium bis(methoxyethoxy)aluminum hydride in toluene solution per mol ofcompound (III).

Compound (I) resulting from the reduction reaction can be isolatedeither as the free base or salified, for example as hydrochloride orphosphate.

The use of sodium bis(methoxyethoxy)aluminum hydride, compared withLiAlH₄ and related hydrides, provides advantages both in terms of safetyand costs of the reduction reaction: in fact, it is not pyrophoric, doesnot react with oxygen and is highly soluble in a number of solvents,such as aromatic hydrocarbons and ethers, which makes it easy to use itand to carry out the reduction reaction in more concentrated solutions.

At the end of the reduction, compound (I) is recovered with the usualextraction, crystallization and/or precipitation techniques, thusremoving the aluminum inorganic salts formed during the reaction.

A particularly effective isolation procedure of compound (I), also whenapplied on the industrial scale, consists in using a strong cationic ionresin to temporarily bind the product on the resin, from which it issubsequently eluted with an ammonia aqueous solution.

A strong cationic resin, such as Amberjet® 1200, suitably regenerated inthe acidic form, or an equivalent commercial resin, is preferably used.

The process of the invention is particularly useful for the preparationof compound (I A) shown in the following Scheme 3.

in which

-   R₁ is C₁-C₄ alkoxy and compound (VI A) is added in amounts of at    least 1 mol per mol of compound (IV).

Compound (I A) can conveniently be transformed into1,4,7,10-tetraazacyclododecane (II A) or the corresponding derivative,with the procedure described in WO 96/28432, or that in WO 98/49151, andpreferably as disclosed in WO 00/53588, by hydrolysis withdiethylenetriamine in water, at pH ranging from 5 to 9, at a temperatureranging from 90 to 120° C., in the presence of 5-10 mol ofdiethylenetriamine per mol of (I A), under inert gas atmosphere or inthe air, for 12-48 h, isolating compound (II A) as thetetrahydrochloride.

Compounds of formula (VI A), in which R₁ is methoxy or ethoxy arepreferred. Particularly preferred is diethyl oxalate, which is added inamounts of at least 1 mol per mol of compound (IV), preferably inabsolute ethanol as reaction solvent and at a temperature of 60-70° C.,for a total reaction time ranging from 6 to 24 hours.

Furthermore, the process shown in the following Scheme 4 is particularlypreferred.

in which R₁ is C₁-C₄ alkoxy and A is a —CHRR₂ group wherein R and R₂have the meanings defined above.

Particularly preferred in step a) of Scheme 4 is the use of compounds(VI), in which R₁ is ethoxy or methoxy and A is a group of formula—CHRR₂ in which R is H and R₂ is Cl or Br.

Particularly preferred is the use of ethyl chloroacetate as compound(VI), in amounts of at least 1 mol per mol of compound (IV), in absoluteethanol, at a temperature from 50 to 70° C., in the presence of at least1 mol of Na₂CO₃ and at least 0.02 mol of NaI per mol of compound (IV)and for a reaction time from 3 to 36 hours.

A further object of the invention is the preparation of bothstereoisomers of formulae (VII) and (VIII), cis and transoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1,2-dione, asshown in Scheme 5.

Compound (IV A), prepared as described above, is reacted using in stepa) the general conditions described above and diethyl oxalate asreagent.

The novel compounds of formula (VII) and (VIII) have been isolated andcharacterized by X ray analysis, as exemplified in the experimentalsection.

The two isomers of formulae (IX) and (X), cis and transoctahydro-2a,4a,6a, 8a-tetraazacyclopent[fg] acenaphthylene-3,4-dione,are prepared analogously, starting from (IV B)(decahydro-diimidazo-[1,2-a:2′,1′-c]pyrazine), isomer of (IV A), withdiethyl oxalate, as shown in Scheme 6.

In this case also the compounds have been recovered and characterized byX ray analysis.

Compound (IX) is already known in literature, whereas compound (X) isnovel.

Literature (see G. Hervè, H. Bernard, Tetrahedron Lett., 40. 2517-2520.1999) described the condensation reaction of glyoxal withtriethylenetetramine, the subsequent cyclization reaction with1,2-dibromoethane to give compound (I A) and the deprotection to1,4,7,10-tetrazacyclododecane (II A). The cited paper also reports the¹³C-NMR spectra of the mixtures of the (IV A) and (IV B) cis and transstereoisomers,

and the conversion conditions of the corresponding isomers at differenttemperatures and experimental conditions.

The same Authors (G. Hervè, H. Bernard et al. Eur. J. Org. Chem., 33-35,2000) reported the preparation of compound (IX) by condensation of (IVB) with diethyl oxalate in ethanol at room temperature as single isomer,whose stereochemistry is established by X rays.

It is also reported that the condensation of compound (IV C) withdiethyl oxalate

under the same conditions does not take place and prolonged heating ofthe solution causes polymeric products to form.

In conclusion, the process of the invention, notwithstanding thecontrary teaching found in literature, provides in good yield compounds(VII) and (VIII) starting from (IVA), and compounds (IX) and (X)starting from (IVB). Furthermore, by the process of the invention it ispossible to isolate and characterize the novel compounds (VII), (VIII)and (X).

A further object of the invention is the process for the preparation ofcompounds (VII) and (VIII) starting from (IV C) as shown in thefollowingScheme 7.

by condensation with diethyl oxalate, even at temperatures below 50° C.

A further object of the invention are compounds of formula (III)

wherein one of Y₁ and Y₂ is —CH₂—CH₂— and the other is —CO—CO— or agroup of formula —CO—CHR—, in which R is H, straight or branched C₁-C₄alkyl, optionally substituted with one more —OPg-protected hydroxygroups in which Pg is a conventional hydroxy-protective groups,preferably benzyl.

Preferred compounds of formula (III) are the compounds of formula (XII)and (XIII)

in which R is H, straight or branched C₁-C₄ alkyl, or aphenylmethoxymethyl group (R=PhCH₂OCH₂—).

Particularly preferred are compounds (VII),cis-octahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1,2-dione,(VIII) transoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1,2-dione, (X)transoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-3,4-dione,

(XII A) decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-3-one,(XIII A)decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]-acenaphthylene-1-one and(XIII B)2-(phenylmethoxymethyl)-decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1-one.

A further object of the invention are the compounds of formula (I),

in which the groups R are both H or one is hydrogen and the other isstraight or branched C₁-C₄ alkyl, optionally substituted with one ormore —OPg-protected hydroxy groups, in which Pg is a hydroxy-protectivegroup.

Particularly preferred is the compound of formula (I B)

2-phenylmethoxymethyldecahydro-2a,4a,6a,8a-tetraazacyclopent[fg]-acenaphthylene, in which R is thephenylmethoxymethyl group (R=PhCH₂OCH₂—).

A further object of the present invention is the compound of formula(XI), trans-decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene.

The following examples illustrate the best experimental conditions tocarry out the process of the invention.

EXPERIMENTAL SECTION

The following procedure was used for the gas-chromatographic analysis:

Instrumentation Hewlett-Packard 5890 gas-chromatographic system,equipped with autosampler series 7673 and HP-3365 unit. Column CP Sil 19CB, 25 m × 0.32 mm, 0.52 mm film Oven temp. program: first isotherm at120° C. for 5 min; ramp 15° C./ min to 260° C.; second isotherm at 260°C. for 12 min Injector Split flow rate 11.5 mL/min Temperature 250° C.Detector FID Temperature 275° C. Hydrogen pressure 1.2 bars Air pressure2.8 bars Column flow rate  1.2 μl/min Carrier gas He₂ Column pressure 20psi Auxiliary gas flow rate 10 mL/min Septum purge flow rate 5 mL/minInjection  1 μl Sample concentration 20 mg/mL Internal standardAcenaphthene Internal standard  10 mg/mL concentr.:

EXAMPLE 1

Preparation of cis/trans ofoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1,2-dione(III)

A) Preparation of 3H,6H-2a,5,6,8a-octahydrotetraaza-acenaphthylene (IVA)

A suitable reactor is loaded, under mild nitrogen stream, with 370.5 gof straight hydrated triethylenetetramine (TETA), 2 kg of water and296.4 g of calcium hydroxide. Then a 9% (w/w) glyoxal aqueous solutionprepared by mixing 290 g of 40% solution with 1 kg of water, stirred innitrogen blanket and cooled to 0-5° C., is added to the resultingsuspension. After completion of the addition, the mixture is kept at 5°C. for 1 h, and filtered through Celite® previously washed with 0.5 kgof water. The filtrate is evaporated to dryness under reduced pressure.

The product is not subjected to purification but is directly used forthe subsequent reaction.

Yield: 98.5% (on dry matter)

GC assay: >75% (% area)

B) Preparation of Compound (III) and Isolation as Hydrochloride

Into a 1 L reactor, kept in nitrogen atmosphere and containing asolution of 50 g (0.297 mol) of compound (IV) prepared as described inexample 1A) in 0.4 L of ethanol, 130 g (0.891 mol) of diethyl oxalateare added. The resulting solution is kept under magnetic stirring at 68°C. for 24 hours, then partially concentrated under reduced pressure to384 g. 86.4 g (0.296 mol) of a 12.5% w/w HCl ethanol solution aredropped into the reaction mixture and kept under magnetic stirring for40 minutes. The suspension is kept for 45 minutes under magneticstirring and the resulting solid is filtered and washed on the filterwith 75 mL of ethanol. The humid solid is dried in a static dryer undervacuum at 40° C. for 12 hours, to obtain 38.4 g (0.146 mol) of thedesired compound with the following analytical characteristics:

GC assay: 94.6% (% area)

Recovery yield: 49%

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 2

Preparation of Compound (III), Free Base

In a suitable reactor, in nitrogen atmosphere, a solution of 50.5 g (0.3mol) of compound (IV) prepared as described in example 1A) in 0.4 L ofethanol and 131.5 g (0.9 mol) of diethyl oxalate are loaded. Thesolution is heated to 68° C. and kept under magnetic stirring at thistemperature for 27 hours. The solvent is evaporated off under reducedpressure to a residue weighing 150 g, and a solution of 123 mL oftoluene and 13 mL of ethanol is added. The resulting suspension is keptunder magnetic stirring for 2 hours, then filtered through porousseptum. The solid is washed with 40 mL of an ethanol/toluene=1/1solution (v/v), then dried in a static dryer under vacuum at 40° C. for12 hours, to obtain 31 g (0.132 mol) of the desired compound having thefollowing analytical characteristics:

GC assay: 95% (% area)

Yield: 44%

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 3

Preparation of Compound (III) by Reaction in Mass

Into a 50 mL round-bottom flask equipped with reflux condenser,thermometer and mechanical stirrer, kept in nitrogen atmosphere, 12 g(0.071 mol) of product prepared as in example 1 A) and 11.9 g (0.078mol) of diethyl oxalate are loaded. The mixture is heated in mass at 65°C. for 5 hours, then added with 1.19 g (0.0078 mol) of diethyl oxalateand heating is continued for 6 hours. The mixture is left to cool toroom temperature and the ethanol formed during the reaction is distilledoff under partial vacuum. The product is purified by chromatography on asilica gel column (eluent: CHCl₃/methanol=8/2 V/V), to obtain 11.2 g(0.050 mol) of the desired compound having the following analyticalcharacteristics:

GC assay: 98 (% area)

Yield: 60%

EXAMPLE 4

Preparation of Compound (III) in the Presence of 2-hydroxypirydine

Into a solution of 50.5 g (0.3 mol) of compound (IV) prepared asdescribed in example 1A) in 0.4 L of ethanol, under magnetic stirringand nitrogen atmosphere, 14.1 g (0.148 mol) of 2-hydroxypyridine and86.80 g (0.594 mol) of diethyl oxalate are added. The solution is keptat 68° C. for 6 hours, then partially concentrated, under vacuumpartial, to a weight of 122 g.

The residual product is added with 170 mL of toluene and 18 mL ofethanol and the suspension is kept under magnetic stirring for 17 hours,then filtered and washed on filter with an ethanol/toluene 1/1 solution(v/v). The product is dried in a static dryer to obtain 41 g (0.179 mol)of the desired compound having the following analytical characteristics:

GC assay: 96.9%

Yield: 60%

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 5

Preparation of Compound (III) in the Presence of Sodium Methoxide

In a solution of 53.5 g (0.318 mol) of compound (IV) in 0.4 L ofethanol, under magnetic stirring and nitrogen atmosphere, 17.2 g (0.318mol) of sodium methoxide are added. The suspension is stirred untilcomplete dissolution, and then is added 92.9 g, (0.636 mol) of diethyloxalate. The mixture is heated to 68° C. and kept at this temperaturefor 1.5 hours. The solution is partially concentrated and then 130 mLethanol is added to the residue at 70° C.

The resulting suspension is kept for 72 hours under mechanical stirringat 23° C. The solid product is filtered, washed with 45 mL of ethanoland dried in a static dryer under partial vacuum to obtain 35.3 g of thedesired compound (0.159 mol) having the following analyticalcharacteristics:

G.C. assay: 95%

Yield: 50%

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 6

Preparation of (VII) cisoctahydro-2a,4a,6a,8a-tetraazacyclo-pent[fg]-acenaphthylene-1,2-dione

The intermediate of formula (IV A), obtained as described in preparation1A), is purified through salification as acetate, according to thefollowing procedure:

15 g (0.09 mol) of compound prepared as described in preparation 1A) aredissolved in 100 g of toluene, then 5.5 g of conc. acetic acid solutionare dropped into the solution and the resulting suspension is stirredfor 10 minutes. The resulting solid is filtered, washed with toluene,and dried under vacuum at 30° C. to obtain 14.1 g of compound (IV C) asmonoacetate.

GC assay: 98% (% area)

Recovery yield: 70%

2 g of the above prepared compound are dissolved in a 10% NaOH solutionand extracted with chloroform. The separated organic phase is dried,filtered and evaporated to a residue weighing 1 g (0.006 mol), which isdissolved in 10 mL of ethanol and added with 2.6 g (0.018 mol) ofdiethyl oxalate. The resulting solution is heated at 70° C. for 12 hoursand concentrated under vacuum to a solid residue. The crude product ispurified by silica gel chromatography, using a CHCl₃/MeOH=8/2 eluentmixture (v/v), to obtain 0.6 g of compound (VII) having the followinganalytical characteristics:

GC assay: 99 (% area)

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 7

Preparation of Compounds (VII) and (VIII), cis and transoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1,2-dione

A) Preparation of (VII) cisoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]-acenaphthylene-1,2-dione.

In a 1 L reactor, in nitrogen atmosphere, 160 mL of absolute ethanol, 21g (0.125 mol) of product prepared as in example 1 A), 6.74 g (0.125 mol)of sodium methoxide and 36.5 g (0.250 mol) of diethyl oxalate areloaded. The solution is heated and kept at 68° C. for 2 hours, thencooled to room temperature and 12.3 g of a 37% HCl solution (0.125 mol)are dropped therein. The resulting suspension is filtered through Celiteand the filtrate is evaporated to dryness to give crude compound (VIII),which will be used for the subsequent isolation of (VIII) (see part B).

The product on the filter is suspended in deionized water and filteredthrough Celite. In the filtrate 6.9 g (0.065 mol) of Na₂CO₃ are addedand the resulting suspension is evaporated to a residue. The solidresidue is suspended in methanol and filtered at 60° C. The resultingsolution is left to spontaneously cool to 23° C. and the solid productobtained from the crystallization is filtered and dried under vacuum at40° C. for 12 hours, to obtain 7.5 g of dry product having the followinganalytical characteristics:

GC assay: 100 (% area)

The ¹H-NMR, ¹³C-NMR, IR, MS and the solid state structure obtained by Xray diffractometry are consistent with the indicated structure.

B) Isolation of (VIII) transoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]-acenaphthylene-1,2-dione

Crude compound (VIII) (see A) is purified by silica gel chromatographyusing a CHCl₃/MeOH/NH₃ eluent mixture. The fractions containing thepurified product are combined and evaporated to a solid residue. Theresulting product is recrystallized from methanol to obtain a product,which is dried under vacuum at 40° C. for 12 hours to yield 1.5 g ofcompound having following analytical characteristics:

GC assay: 100 (% area)

The ¹H-NMR, ¹³C-NMR, IR, MS and the solid state structure obtained by Xray diffractometry are consistent with the indicated structure.

EXAMPLE 8

Preparation and Isolation of (X) transoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-3,4-dione

A) Preparation of decahydro-diimidazo-[1,2-a:2′,1′-c]pyrazine (IV B)

In a suitable 2 L reactor, maintained under nitrogen atmosphere, 50 g(305 mmol) of straight hydrated TETA and 1 L of absolute ethanol areloaded. To the solution 44.5 g (305 mmol) of a 40% glyoxal solution areadded. After completion of the addition, the solution is kept undermagnetic stirring at 23° C. for 17 hours. The resulting solution isconcentrated under partial vacuum to an oily residue.

GC assay: 75% (% area)

B) Preparation and Isolation of Compound (X)

In a 0.25 L round-bottom flask equipped with mechanical stirrer andthermometer, under nitrogen atmosphere, 5.5 g (0.0326 mol) of compound(IV B) prepared as described above in Example 8 A), 80 mL of absoluteethanol, 0.88 g (0.0163 mol) of sodium methoxide and 2,38 g (0.0163 mol)of diethyl oxalate are loaded. The resulting solution is heated at 68°C. for 8 hours and, after partial concentration under vacuum, is left tospontaneously cool to 23° C. The crystallized solid product is filteredand recrystallized from methanol. The product is recrystallized,filtered and dried under vacuum in a static dryer at 40° C. for 12hours, to yield 0.5 g of the desired compound having the followinganalytical characteristics:

GC assay: 100 (% area)

The ¹H-NMR, ¹³C-NMR, IR, MS and the solid state structure obtained by Xray diffractometry are consistent with the indicated structure.

EXAMPLE 9

Preparation and Isolation of (IX) cisoctahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-3,4-dione

In a 1 L reactor equipped with mechanical stirrer, thermometer, refluxcondenser and nitrogen blanket, 30 g (0.178 mol) of product prepared asin example 8 A), 225 mL of absolute ethanol and 13 g (0.089 mol) ofdiethyl oxalate are loaded. The solution is heated and kept at 68° C.for 18 hours, and then 2.6 g (0.0178 mol) of diethyl oxalate are addedand the solution is kept at 68° C. for 4 hours. The solution is left tocool to 23° C. and the crystallized solid is filtered and recrystallizedfrom methanol. The resulting product is dried at 40° C. for 12 hours toa weight of 6.2 g (0.0279 mol) and has the following analyticalcharacteristics:

GC assay: 100 (% area)

The ¹H-NMR, ¹³C-NMR, IR, MS and the solid state structure obtained by Xray diffractometry are consistent with the indicated structure.

EXAMPLE 10

Preparation ofdecahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1-one (XIII A)

In a 1 L round-bottom flask containing 0.2 L of ethanol and 18 g (0.107mol) of compound (IV A) prepared as in example 1 A, are loaded 22.7 g(0.214 mol) of Na₂CO₃, 1.6 g (0.0107 mol) of NaI and 26.2 g (0.214 mol)of ethyl chloroacetate. The resulting suspension is stirred for 24 hoursat 23° C., then filtered through porous septum and the resultingfiltrate is evaporated to dryness.

In a 0.25 L round-bottom flask equipped with mechanical stirrer, refluxcondenser and nitrogen blanket and thermometer, are placed 16 g of theabove prepared product, 60 mL of ethanol, and 1.47 g of 2-pyrydinol(0.016 mol). The resulting solution is refluxed for 48 hours. Thesolution is cooled and evaporated to dryness. The residue is purified bysilica gel chromatography with a CHCl₃/MeOH=95/5 (v/v) eluent solution.The fractions containing the purified product are combined andconcentrated under partial vacuum to a solid residue, to obtain 10 g ofpurified compound having the following analytical characteristics:

Yield 45%

GC assay: 80 (% area)

EXAMPLE 11

Preparation of2-(phenylmethoxymethyl)-decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene-1-one(XIII B)

In a 250 mL round-bottom flask 100 mL of ethanol and 10 g (0.059 mol) ofcompound (IV A) prepared as in example 1A are loaded, then 6.25 (0.059mol) of sodium carbonate, 0.45 g (0.03 mol) of NaI and 21.4 g (0.088mol) of ethyl 3-benzyloxy-2-chloro-propionate are added. The suspensionis stirred for 36 hours at room temperature, then filtered. The solid iswashed with 30 mL of ethanol. The filtrate is partially concentrated to120 g and added with 2.66 (0.029 mol) of 2-pyrydinol. The resultingsolution is refluxed for 48 hours, then evaporated and the residue ispurified by silica gel chromatography, eluting withchloroform/methanol=9/1. The fractions containing the purified productare combined and evaporated to a residue, to obtain 7.4 g of compound.

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 12

Preparation of decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene(I A)

In a 1 L round-bottom flask containing 100.8 g (70% in toluene; 0.349mol) of Vitride® in 0.2 L of toluene, kept in nitrogen atmosphere andmagnetic stirring, are added 19.4 g (0.087 mol) of compound (III),prepared as in example 5. The resulting suspension is heated and kept at112° C. for 1 hour.

The solution is left to cool to 22° C., then 58 mL of a 5% w/w NaOHaqueous solution are slowly dropped therein. The two resulting phasesare separated and the aqueous phase is extracted with toluene. The firstseparated organic phase and those deriving from the toluene extractionare combined, evaporated to dryness, and the residue is dissolved in 80mL of deionized water. The aqueous solution is percolated onto a columncontaining 165 mL of Amberjet 1200® cationic resin, previouslyregenerated in the H⁺ form. Water is at first percolated on the resinbed to neutral eluate, and then a 2.5% NH₄OH solution is percolated. Theammonia fractions containing the product are evaporated to dryness. Thesolid residue is extracted at 50° C. with n-hexane and the resultingsolutions are combined and further evaporated under partial vacuum to aresidue. The resulting solid product is dried in the presence of P₂O₅ toobtain 14.2 g (0.073 mol) of compound having the following analyticalcharacteristics:

Tit. G.C.: 100%

Yield: 84%

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 13

Preparation of decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene(IA) starting fromdecahydro-2a,4a,6a,8a-tetraazacyclo-pent[fg]acenaphthylene-1-one (XIIIA)

In a 0.1 L round-bottom flask containing 10 mL of toluene and 2.8 g (70%toluene; 0.0096 mol) of Redal®, maintained under mechanical stirring andnitrogen blanket, 1 g (0.004 mol) of the compound of example 10 is addedat 45° C. The solution is heated to 100° C. for 1 hour, then cooled toroom temperature and added with 1.5 mL of 5% NaOH. The two resultingphases are separated and the aqueous phase is extracted with toluene.The combined organic phases are concentrated under vacuum to a solidresidue. The resulting product is purified by silica gel chromatographyeluting with a CHCl₃/MeOH=8/2 mixture (v/v). The fractions containingthe purified product are combined and concentrated to a solid residueweighing 0.60 g.

Yield: 77%

GC assay: 100 (% area)

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 14

Preparation of2-phenylmethoxymethyl-decahydro-2a,4a,6a,8a-tetraazacyclo-pent[fg]acenaphthylene

Compound (I B) is obtained by using compound (XIII B) as startingproduct and the reductive conditions as described in example 13.

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

EXAMPLE 15

Preparation oftrans-decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene (XI)

Compound (XI) is isolated from the isomeric cis/trans mixture obtainedfrom example 12, by silica gel chromatography, eluting withCHCl₃/CH₃OH=9:1. The resulting compound has the following analyticalcharacteristics:

GC assay: 100 (% area)

The ¹H-NMR, ¹³C-NMR, IR and MS spectra are consistent with the indicatedstructure.

1. A process for the preparation of the compounds of general formula (I)

in which the groups R are both hydrogen, or one is hydrogen and theother is a straight or branched C₁-C₄ alkyl group, optionallysubstituted with one or more —OPg-protected hydroxy groups, in which Pgis a hydroxy-protecting group, which process comprises: step a) reactinga compound of general formula (IV),

in which, both of the groups X₁ are hydrogen or both are CH₂ and both ofthe groups X₂ are hydrogen or both are CH₂, provided that when thegroups X₁ are hydrogen, the groups X₂ form a —CH₂CH₂— and when thegroups X₁ are a —CH₂CH₂— group, then the groups X₂ are hydrogen, with acompound of general formula (VI)

in which A is a group of formula —COR₁ or —CHRR₂ wherein R has themeaning defined above, R₁ is halogen or a C₁-C₄ alkoxy group and R₂ is aleaving group such as halogen or sulfonyloxy, in at least unitary molarratio, at a temperature above 50° C.; step b) reducing the compoundsobtained from step a), having general formula (III)

in which one of Y₁ or Y₂ is —CH₂—CH₂— and the other is —CO—CO— or agroup of formula —COCHR, wherein R has the meaning defined above, in thepresence of an amido-reducing agent.
 2. A process as claimed in claim 1wherein in the compounds of formula (III), R is H or straight orbranched C₁-C₄ alkyl, optionally substituted with one or more —OPggroups in which Pg is benzyl.
 3. A process as claimed in claim 1 whereinthe reaction of compound of formula (IV) with compound of formula (VI)is carried out under inert gas atmosphere, using at least 1 mol ofcompound (VI) per mol of compound (IV), in the presence of a solventselected from: aromatic inert, aprotic dipolar, or straight or branchedC₁-C₄ alcohols and polyethers.
 4. A process as claimed in claim 3,wherein the solvent is selected from the group consisting of: toluene,dimethylacetamide, dimethylformamide, N-methylpyrrolidone, DMSO, C₁-C₄alcohols, glyme and diglyme.
 5. A process as claimed in claim 1, whereinthe reactants are not dissolved in a reaction solvent.
 6. A process asclaimed in claim 1, in which step a) is carried out in the presence ofalkali or alkaline-earth metal salts of anions of straight or branchedC₁-C₄ alcohols, or of heterocyclic aromatic bases, as catalysts.
 7. Aprocess as claimed in claim 1, in which step a) is carried out in thepresence of a catalyst selected from the group consisting of sodiummethoxide, sodium ethoxide, or one of the compounds of formulae:


8. A process as claimed in claim 7, wherein the catalyst is sodiummethoxide or 2-hydroxypyridine, in amounts ranging from 0.01 to 2 molper mol of compound (IV).
 9. A process as claimed in claim 1, whereincompound of formula (III) is recovered upon completion of the reaction,either as a salt with an inorganic acid selected from the groupconsisting of hydrochloric, sulfuric and phosphoric acids, or as thefree base.
 10. A process as claimed in claim 1, wherein the reduction ofcompound (III) is carried out in dry medium and under inert atmosphere,using the amido-reducing agent selected from the group consisting of:sodium bis(methoxyethoxy)aluminum hydride, LiAlH₄, NaBH₄, borane or thetetrahydrofuran or dimethyl sulfide adducts thereof or by catalytichydrogenation on platinum oxide and in HCl solution.
 11. A process asclaimed in claim 10, wherein are used sodium bis(methoxyethoxy)aluminumhydride or catalytic hydrogenation on platinum oxide in HCl aqueoussolution.
 12. A process as claimed in claim 11, wherein the reducingagent is sodium bis(methoxyethoxy)aluminum hydride, in amounts rangingfrom 3 to 4 mol per mol of compound (III), at a reaction temperatureabove 35° C.
 13. A process as claimed in claim 9, wherein compound offormula (I) is isolated as free base or salified as hydrochloride orphosphate.
 14. A process as claimed in claim 13, wherein the compound offormula (I) is isolated at the end of the process by using a cationicion exchange resin.
 15. A process as claimed in claim 1 wherein is useda compound of formula (VI) is

wherein R₁ is a C₁-C₄ alkoxy group.
 16. A process as claimed in claim15, wherein in compound of formula (VI A), R₁ is methoxy or ethoxy. 17.A process as claimed in claim 16, wherein compound (VI A) in amounts ofat least 1 mol per mol of compound (IV), in absolute ethanol as reactionsolvent and at a temperature of 60-70° C.
 18. A process as claimed inclaim 1, wherein is used a compound (VI), in which R₁ is a C₁-C₄ alkoxygroup and A is a —CHRR₂ group wherein R and R₂ have the meanings definedabove.
 19. A process as claimed in claim 18, wherein in the compound offormula (VI), R₁ is methoxy or ethoxy, and A is a group of formula—CHRR₂ in which R is H and R₂ is Cl or Br.
 20. A process as claimed inclaim 19, wherein in step a) ethyl chloroacetate the compound of formula(VI), and is used in amounts of at least 1 mol per mol of compound (IV),in absolute ethanol, at a temperature ranging from 20 to 70° C., in thepresence of 1 mol of Na₂CO₃ per mol of compound (IV) and for a reactiontime ranging from 3 to 36 hours.
 21. Compounds of general formula (III),

wherein one of Y₁ or Y₂ is —CH₂—CH₂— and the other is a group of formulaCOCHR wherein R is H or straight or branched C₁-C₄ alkyl, optionallysubstituted with one more —OPg groups in which Pg is as defined above,Y₁ is CO—CO and Y₂ is CH₂—CH₂.
 22. Compounds as claimed in claim 21wherein R is H, straight or branched C₁-C₄ alkyl, optionally substitutedwith one or more benzyl-protected hydroxy groups.
 23. A compound asclaimed in claim 21, of formulae (XII) and (XIII)


24. A compound as claimed in claim 23, of formulae (XII A), (XIII A) and(XIII B)


25. Compounds of formula (I)

wherein one of the groups R is hydrogen and the other is straight orbranched C₁-C₄ alkyl, optionally substituted with one or more groups—OPg in which Pg is a hydroxy-protecting group.
 26. The compound offormula (I B)

which is2-phenylmethoxymethyl-decahydro-2a,4a,6a,8a-tetraazacyclo-pent[fg]acenaphthylene.27. The compound of formula (XI)

which istrans-decahydro-2a,4a,6a,8a-tetraazacyclopent[fg]acenaphthylene.
 28. Acompound as claimed in claim 21, of formula (VII) or (VIII)


29. A compound of the formula (X)